基本上，我的问题是我不确定如何从用户设置无限输入数组。 目前，只有当用户准确输入6个主题时，计算才会顺利进行，但如果输入的主题少于或大于6，则计算不正确。 不知何故，我想让输入无限制。
这是我到目前为止所做的：
主要课程
import javax.swing.*;
public class CGPAMain extends JFrame
{
public static void main(String[] args)
{
JFrame frame = new JFrame("GPA Calculation");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MainPage panel = new MainPage();
frame.getContentPane().add(panel);
frame.pack();
frame.setVisible(true);
}
}
其他类别
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MainPage extends JPanel
{
//declare GUI elements
private JLabel subjectLabel, cHoursLabel, gradeLabel;
private JTextField subject, cHours;
private JButton addSubjectButton, calcGPAButton, clearAllButton;
private JTextArea tArea;
private JComboBox grade;
//declare array to store and collect user input value
String[] subjectArray = new String[6];
String[] gradeArray = new String[6];
int[] cHoursArray = new int[6];
double[] gradeValue = { 4.00, 3.67, 3.33, 3.00, 2.67, 2.33, 2.00, 1.67, 1.33, 1.00, 0.00 };
String[] gradeLetter= { "A", "A-", "B+", "B", "B-", "C+", "C", "D", "D-", "E", "F"};
public MainPage()
{
setLayout (null);
setPreferredSize (new Dimension(500, 500));
setBackground (Color.orange);
//Properties of GUI elements
subjectLabel = new JLabel ("Subject Name: ");
subject = new JTextField (33);
subject.addActionListener (new TempListener());
gradeLabel = new JLabel ("Grade: ");
grade = new JComboBox (gradeLetter);
grade.addActionListener (new TempListener());
cHoursLabel = new JLabel ("Credit Hours: ");
cHours = new JTextField (1);
cHours.addActionListener (new TempListener());
addSubjectButton = new JButton("Add Another Subject");
addSubjectButton.addActionListener(new TempListener());
calcGPAButton = new JButton("Calculate GPA");
calcGPAButton.addActionListener(new TempListener());
clearAllButton = new JButton("Clear All");
clearAllButton.addActionListener(new TempListener());
tArea = new JTextArea(5, 5);
tArea.setEditable(false);
add (subjectLabel);
add (subject);
add (gradeLabel);
add (grade);
add (cHoursLabel);
add (cHours);
add (addSubjectButton);
add (calcGPAButton);
add (clearAllButton);
add (tArea);
//Position of GUI elements
subjectLabel.setBounds (20, 20, 150, 20);
subject.setBounds (120, 20, 350, 20);
gradeLabel.setBounds (20, 50, 50, 20);
grade.setBounds (120, 50, 50, 20);
cHoursLabel.setBounds (20, 80, 100, 20);
cHours.setBounds (120, 80, 50, 20);
addSubjectButton.setBounds (20, 120, 200, 30);
calcGPAButton.setBounds (300, 440, 175, 30);
clearAllButton.setBounds (20, 440, 120, 30);
tArea.setBounds (20, 170, 450, 250);
}
private class TempListener implements ActionListener
{
//---------------------------------------------------------------------------
// Performs the conversion when the enter key is pressed in the text field.
//---------------------------------------------------------------------------
double tCrPoints = 0.00, tCrHours = 0.00, tGPA = 0.00;
String status;
public void actionPerformed(ActionEvent event)
{
if (event.getSource() == addSubjectButton)
{
for (int i=0; i<6; i++)
{
subjectArray[i] = subject.getText();
gradeArray[i] = (String) grade.getSelectedItem();
cHoursArray[i] = Integer.parseInt(cHours.getText());
}
tArea.append (subject.getText() + "\t\t\t" +
grade.getSelectedItem() + "\t" +
cHours.getText() + "\n");
subject.setText("");
cHours.setText("");
}
if (event.getSource() == calcGPAButton)
{
for (int i=0 ; i<gradeArray.length; i++)
{
for (int j=0; j<gradeLetter.length; j++)
{
if(gradeArray[i].equals(gradeLetter[j]))
{
tCrHours += cHoursArray[i];
tCrPoints += gradeValue[j] * cHoursArray[i];
}
}
}
tGPA = tCrPoints/tCrHours;
if (tGPA >= 2)
status = ("Pass");
else
status = ("Fail");
//Output for text area
tArea.setText("Total Credit Points : " + tCrPoints + "\n" +
"Total Credit Hours : " + tCrHours + "\n\n" +
"Grade Point Average (GPA) : " + tGPA + "\n" +
"Status : " + status);
}
if (event.getSource() == clearAllButton)
{
tArea.setText("");
cHours.setText("");
grade.setSelectedIndex(0);
tCrHours = 0.00;
tCrPoints = 0.00;
}
}
}
}
答案 0 :(得分：3)
您正在寻找ArrayList<E>
答案 1 :(得分：3)
你很好地将main()从GUI和应用程序的其余部分分开，但我认为你应该进一步将GUI从计算代码中分离出来。
考虑一个更大的问题：为什么GUI JPanel知道成绩和GPA？ JPanel的工作是知道如何在框中呈现GUI元素并将输入事件路由到正确的窗口小部件对象。
我相信如果你拆分代码来管理代码中的等级来处理GUI，你的代码将更易于维护并且更具有可塑性。告诉GUI将值更新为model与模型从GUI中轮询数据值之间总是会有一点粗略的优势，但您可以定义该界面以最好地满足您的需求：可能是一个GPA对象，使用SLaks's recommended ArrayList<E>来存储知道姓名，成绩，课程日期等的个别Subject个对象。（可能只是（name }，grade）元组，因为到目前为止它很短而且很甜。）
您的GPA对象可以导出界面：public void addSubject(String className, String grade)和public double getGPA()。您的GUI可以调用此界面来添加新类并检索GPA以供显示。
我意识到这是一个比你想要的更剧烈的重写。它甚至没有立即解决您的问题。但我相信，GPA代码在单独查看时，看起来比目前埋在GUI代码中的代码更容易被操纵。
答案 2 :(得分：2)
您应该查看ArrayList，Vector甚至LinkedList以了解您所寻求的功能。这是一个tutorial，解释了如何使用ArrayList。
这个想法很简单：ArrayList将负责增加一个内部数组来存储它的元素，当你不断添加元素时，它会自动增长以适应它们。严格来说，大小不会无限，但最多2 ^ 31-1个位置（假设你有足够的内存），对于大多数实际情况来说，我应该绰绰有余。
编辑：
对于您的特定示例：
// create an ArrayList
ArrayList<Double> gradeValue = new ArrayList<Double>();
// add elements to the ArrayList
gradeValue.add(4.00);
gradeValue.add(3.67); // etc.
// iterating over the ArrayList
for (int i = 0; i < gradeValue.size(); i++) {
double value = gradeValue.get(i);
// etc.
}
答案 3 :(得分：1)
使用散列图包含所有成绩，并使用数组列表来包含您获得的小时和成绩。这是对你所拥有的内容的快速重写。
public class MainPage extends JPanel {
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
private JLabel subjectLabel, cHoursLabel, gradeLabel;
private JTextField subject, cHours;
private JButton addSubjectButton, calcGPAButton, clearAllButton;
private JTextArea tArea;
private JComboBox grade;
List<String> gradeArray = new ArrayList<String>();
List<Integer> cHoursArray = new ArrayList<Integer>();
Map<String, Double> grades = new HashMap<String, Double>();
public MainPage() {
this.populateGrades();
setLayout(null);
setPreferredSize (new Dimension(500, 500));
setBackground (Color.orange);
subjectLabel = new JLabel ("Subject Name: ");
subject = new JTextField (33);
subject.addActionListener (new TempListener());
gradeLabel = new JLabel ("Grade: ");
grade = new JComboBox (grades.keySet().toArray());
grade.addActionListener (new TempListener());
// ... THE REST OF YOU CODE ... //
}
private void populateGrades() {
grades.put("A", 4.00);
grades.put("A-", 3.67);
grades.put("B+", 3.67);
grades.put("B", 3.67);
grades.put("B-", 3.67);
grades.put("C+", 3.67);
grades.put("C", 3.67);
grades.put("D", 3.67);
grades.put("D-", 3.67);
grades.put("E", 3.67);
grades.put("F", 3.67);
}
private class TempListener implements ActionListener {
double tCrPoints = 0.00, tCrHours = 0.00, tGPA = 0.00;
String status;
public void actionPerformed(ActionEvent event) {
if (event.getSource() == addSubjectButton) {
// Not sure what you are trying to do here, you are basically setting the 3 arrays identical
// subject.getText() = 1 ==> subjectArray[1,1,1,1,1,1]
// Do not see the point of this at all
/* for (int i=0; i<6; i++) {
subjectArray[i] = subject.getText();
gradeArray[i] = (String) grade.getSelectedItem();
cHoursArray[i] = Integer.parseInt(cHours.getText());
} */
gradeArray.add(grade.getSelectedItem().toString());
cHoursArray.add(Integer.parseInt(cHours.getText()));
tArea.append (subject.getText() + "\t\t\t" + grade.getSelectedItem() + "\t" + cHours.getText() + "\n");
subject.setText("");
cHours.setText("");
}
if (event.getSource() == calcGPAButton) {
for (String grade : gradeArray) {
tCrPoints += grades.get(grade);
}
for (Integer hour : cHoursArray) {
tCrHours += hour;
}
tGPA = tCrPoints/tCrHours;
if (tGPA >= 2) {
status = ("Pass");
} else {
status = ("Fail");
}
tArea.setText("Total Credit Points : " + tCrPoints + "\n" +
"Total Credit Hours : " + tCrHours + "\n\n" +
"Grade Point Average (GPA) : " + tGPA + "\n" +
"Status : " + status);
}
if (event.getSource() == clearAllButton) {
tArea.setText("");
cHours.setText("");
grade.setSelectedIndex(0);
tCrHours = 0.00;
tCrPoints = 0.00;
}
}
}
}